Side thrust limiter for ring and pinion gearing

ABSTRACT

A limiting means that prevents excessive lateral deflection of a ring gear in opposition to the side thrust imposed by applying torque through interengagement with a pinion gear, and in the form of a closely adjustable thrust bearing engageable with the side of the ring gear as and when it is laterally deflected so as to restrict said deflection and thereby prevent undue damaging stresses otherwise imposed upon the bearings and supporting structure such as the gear case.

United States Patent 1 Halibrand [451 July 17,1973

[ SIDE THRUST LIMITER FOR RING AND PINION GEARING [76] Inventor: HenryT. Halibrand, 1506 W. 228th St., Torrance, Calif. 90501 [22] Filed: Dec.30, 1971 [21] Appl. No.: 214,234

[52] US. Cl. 74/410, 74/424 [51] Int. Cl. F16h 57/00, F16h 1/18 [58]Field of Search 74/410, 409, 424

[56] References Cited UNITED STATES PATENTS 1,847,611 3/1932 Hodgkinson74/410 3,252,348 5/1966 Folkerts 74/409 3,434,374 3/1969 Barwig et al74/410 X 3,557,634 l/l97l Bixby 74/694 UX Prim ary Examiner-Leonard H.Gerin Att0rney--William l-l. Maxwell 5 7] ABSTRACT A limiting means thatprevents excessive lateral deflection of a ring gear in opposition tothe side thrust imposed by applying torque through interengagement witha pinion gear, and in the form of a closely adjustable thrust bearingengageable with the side of the ring gear as and when it is laterallydeflected so as to restrict said deflection and thereby prevent unduedamaging stresses otherwise imposed upon the bearings and supportingstructure such as the gear case.

21 Claims, 3 Drawing Figures PATENTEL JUL 1 71973 3, 745, 848

' SHEET 2 BF 2 BACKGROUND Ring and pinion gearing is the subject of thisinvention, and which takes a wide variety of forms and uses. A mostwidely known use of such gearing is in the differential drive of motorvehicles, and it is here that great stresses are involved. Not only isthere the application of power at high torque rates, but there is theapplication of power surges and impact loads in addition thereto.Whatever the case may be, there is the application of strenuous forceswhich are applied without prediction and far in excess of the normalloads and pressures for which a gear case is expected to withstand.Consequently, it is not uncommon for the gear case housing a ring andpinion gear set to be broken apart, due to excessive side thrusts whichcauses and which is aggreviated by the separation of the intermeshinggear teeth, and all of which contributes to the augmenting of strainsresulting in the ultimate failure of the structural support of the gearcase housing. In the event of such a housing failure which invariablyresults in displacements of the ring and pinion axes, major repairsand/or complete replacement becomes necessary.

FIELD OF INVENTION The operation of high performance vehicles, namelyrace cars, requires the use of highly engineered components among whichare the drive axle and ring and pinion unit. These units are commonlyreferred to as rear ends in rear wheel drive cars and they vary widelydepending upon the use to which they are to be put. That is, they areprovided with and without differential gearing, in which case the axlesare either split or straight through. Many championship race cars areprovided with straight through tubular axles, and it is this type ofcompetition ring and pinion unit which is shown herein, although it isto be understood that the thrust limiting idea of means herein disclosedis equally applicable to other ring and pinion gear units.

Ring and pinion gear cases of the type under consideration are oftenmade of light weight metals stressed to safety factors compatible withnormal expected use. Reference is made to race car transmission and axlehousings which are put to strenuous use subject to unexpected loads inexcess of those designed for, and particularly to side thrust loads onthe ring gear which often result in damaging deflections. It is ageneral object of this invention to provide a side thrust limiter ingear cases of the type under consideration which prevents excessivedeflections resulting from side thrusts imposed upon the ring gear caseto withstand the otherwise damaging effects. With the side thrustlimiter herein disclosed the interengagement of the ring and pinion gearteeth is not permitted to separate in a man- 'ner to augment the sidethrust forces that are applied,

and consequently there is a substantially lesser tendancy for the teethto climb out of said interengagement; thereby limiting the damagingeffect of the initial side thrust.

An object of this invention is to provide a side thrust limiter that isadapted to be incorporated in a gear case to engage a ring gear andthereby restrict its lateral deflection. With the present invention, thering gear is normally free to revolve without frictionally engaging theside thrust limiter; however, side thrust applied to the ring gear whentorque is applied at the pinion gear will cause deflection andconsequent engagement of the ring gear with the side thrust limiter. Itis the marginal side face of the ring gear which engages with the sidethrust limiter when deflection occurs.

It is another object of this invention to provide a side thrust limiterof the character thus far referred to and which is adjustable relativeto the ring gear location, axially independent of the pre-load and/oraxial position of said ring gear.

SUMMARY OF INVENTION The present invention is incorporated in a gearcase B that houses a ring and pinion gear set, in order to protect thecase when excessive torque is applied to the gear set, and which willenable the gear case to withstand greater side thrust loads by resistinglateral movement of the ring gear R relative to the pinion gear P. Aswill be observed, the positioning and the deflection of the pinion gearP is not as great a problem, since it is of relative small diameter andis located adjacent the support bearings. However, the lateral movementat the periphery of the ring gear R is a great problem inasmuch astorque applied through the pinion gear P results in side thrust andconsequent lateral deflection at said periphery. Therefore, and inaccordance with this invention, I have provided the side thrust limiterX which is engageable with the marginal portion of the ring gear R inopposition to the pinion gear P engageably therewith. In the preferredform, the side thrust limiter X is adjustable and in the form of abearing 10 having a thrust face 11 that is selectively positioned ascircumstances require to have interface engagement with the side face ofthe ring gear R as and when it is deflected laterally thereagainst.Accordingly, the ring gear R is rotatably joumaled in the case B upon anaxle A supported in carrier bearings 12 which operate in the usualmanner to take the normal axial and radial thrust loads imposed uponsaid ring gear R.

DRAWINGS The various objects and features of this invention will befully understood from the following detailed description of the typicalpreferred form and application thereof, throughout which descriptionreferences is made to the accompanying drawings, in which:

FIG. I is a side elevation of a ring and pinion gear unit embodying thepresent invention.

FIGS. 2 and 3 are each enlarged detailed fragmentary views taken asindicated by lines 2-2 and 3-3 on FIG. 1 respectively.

PREFERRED EMBODIMENT Referring now to the drawings, the gear case B isshown as a quick change unit involving a center section -15 ofcylindrical form having spaced parallel side faces 16 in planes normalto a central axis on which the drive axle A is to operate. The centersection is therefore characteristic of an open-ended barrel closed bymeans of opposite side plates C and D in which the carrier bearings 12are retained to take the normal axial and radial thrust loads of theaxle A. As shown, studs 17 project from the opposite faces 16 to receivethe side plates C and D, secured thereto by nuts 18 thereby closing thegear case.

The axle A is driven by means of pinion shaft S which places the piniongear P within the center section IS in a position to engage one sidemarginal portion of the ring gear R carried within the center sectionadjacent the periphery of said pinion gear. That is, the ring and piniongears are complementary and they are provided with intermeshing teethwhich can vary as to form and axial placement. For example, the toothforms can be straight or helical and the gear axes can intersect or behypoid; and in general the ring and pinion arrangement can be asrequired wherein the gear engagement is angular and such as to imposeside thrust on the ring gear R when torque is applied through the piniongear P. It is to be understood that inefficiencies resulting in the sidethrust with which this invention is concerned are to be minimum butnevertheless occur; and it is the ring gear R that is rotatably capturedin position against axial movements by the side plates C and D and thecarrier bearings 12 and which is subjected to side loads at itsperiphery tending to separate the toothed portions of the two gears Pand R.

The quick change feature of the gear case B is shown and illustrates apractical application of this invention as applied to race car driveunits. As shown, a drive shaft 20 extends through the lower portion ofthe center section 15, supported upon spaced bearings 21 and 22, whilethe pinion shaft S extends into the cylindrical case on spaced bearings23 and 24, the two shafts being on spaced parallel axes. A housing 25extends from the case B surrounding the bearings 22 and 24 to housechangeable drive gears 26 and 27 by which the drive shaft 20 propels thepinion shaft S. A quickly removeable cover plate 28 is secured by meansof nuts 30 to studs 29 projecting from the housing 25; and all to theend that the pinion gear P is driveable to impose torque loads upon thering gear R.

In accordance with this invention and the general object thereof toreinforce the thrust capabilities of the gear transfer unit, the piniongear P is immoveably journaled in the center section by means of astraddle-mount 35 made as part of said center section and preferablyintegral therewith. In practice, the straddlemount 35 is part of thecasting which forms the center section 15 and embraces the pinion gear Pwhile exposing one side thereof which intermeshes with the opposing sidemarginal portion of the ring bear R. The straddle-mount 35 features aradial thrust bearing 36 carrying the terminal end of the pinion gear Pand spaced from the bearing 23 and between which the pinion gearoperates. The straddle-mount 35 also features a thrust face 27, parallelwith or coplanar with the center section side face 16 and which isengaged by a complementary coplanar boss 39 on the inside of side plateC. Upon assembly of the side plate C with center section 15 thestraddle-mount 35 is structurally reinforced and prevented fromdeflecting away from the ring gear R.

In accordance with the present invention, the side thrust limiter X isprovided to restrict lateral deflection of the marginal toothed portionof the ring gear R and thereby reinforces the thrust capabilities of thegear transfer unit comparable with the aformentioned reinforcementafiorded by the straddle-mount 35. In practice, the bearing 10 in whichthe side thrust limiter X is preferably embodied is carried by the sideplate D and with its thrust face 11 oppsing the straddle-mount 35 andpinion gear P; the marginal portion of the ring gear R being disposedtherebetween. That is, one side face of the ring gear R is toothed andintermeshed with the pinion gear P while the other side face 40 is in aplane normal to the rotational axis of the ring gear and engageable withthe thrust face 11 of bearing 10. Upon assembly of side plate D with thecenter section 15, the marginal side face 40 of the ring gear R remainsfree, as the bearing 10 is moveable and is subsequently brought intonear proximity to the side face 40.

The side thrust limiter X is adjustably carried by a boss 48 in the sideplate D to be moved in a direction parallel to the rotational axis ofaxle A. Since the marginal portion of the ring gear R is radiallydisplaced from the axis thereof, the bearing 10 is correspondinglydisplaced to occur opposite the load center of the ring and pinioninterengagement. In its preferred form, the bearing 10 is a threadedelement of substantial diameter that is rotatably secured by a lock nut47. The bearing element 10 is threadedly engaged through the boss 48with a head 46 at the exterior of the side plate D. Therefore, thethrust face 11 of the side thrust limiter X is adjustable into near ortouching engagement with the side face 40, independently of the pre-loadand axial positioning of the ring gear R, after which the lock nut 47 istightened to fix the proximity of the thrust bearing face 11 to the face40.

From the foregoing it will be seen that a condition of equilibrim isestablished between the side plates C and D which incorporate the bosses38 and 48 and which work in opposition to reinforceably oppose thestraddle-mount 3S and side face 40 respectively. All radial thrustgenerated by torque applied through the pinion gear I is carried by thebearings 23 and 36, and the side thrust reaction thereof resulting indeflection of the ring gear R is taken by the side thrust bearing face11. During normal operation of the ring and pinion gears there will beno engagement of the face 40 with the side thrust bearing face 11;however, if and when the side thrust results in a deflection thatexceeds the proximity clearance of the side thrust bearing face 11 therewill be a restrictive engagement thereof with face 40. In practice, suchrestrictive engagements will be few and momentary when experienced as aresult of power surges and/or impact loads, and consequently the wear offace 40 and of side thrust bearing face 1 1 will be negligible; and saidwear can be compensated for from time to time by suitable adjustmentsmade from the exterior of the unit, as described.

Having described only a typical preferred form and application of myinvention, 1 do not wish to be limited or restricted to the specificdetails herein set forth, but wish to reserve to myself anymodifications or variations that may appear to those skilled in the art:

I claim:

1. In combination with a transmission case having a ring gear and apinion gear, said ring and pinion gears being rotatably journaled inbearings carried in the case to take the normal axial and radial thrustloads, the ring gear having a circumferentially disposed marginalportion intermeshed with the pinion gear at one side and a coextensiveface at the opposite side; and a side thrust limiter engageable withsaid opposite side face to prevent separation of the intermeshed gearsby restricting lateral deflection at the marginal portion of said ringgear and comprising a bearing with a thrust face positioned in closeproximity to the coextensive face at the opposite side of said marginalportion of the ring gear, thereby reinforcing the combination againstthrust loads causing lateral deflection of the marginal portion of thering gear and interface engagement of said opposite side face thereofwith said side thrust limiter.

2. The combination of claim 1 wherein the side thrust limiter ispositioned opposite the load center of the ring and pinioninterengagement.

3. The combination of claim 1 wherein the coextensive face at theopposite side of the ring gear is in a plane normal to the axis ofrotation of said ring gear and the thrust face of the side thrustlimiter bearing is juxtapposed parallel to said coextensive face.

4. The combination of claim 1 wherein the coextensive face at theopposite side of the ring gear is in a plane normal to the axis ofrotation of the said ring gear and the thrust face of the side thrustlimiter bearing is juxtapposed opposite the load center of the ring andpinion interengagement parallel to said coextensive face.

5. The combination of claim 1 wherein the side thrust limiter ispositioned opposite the load center of the ring and pinioninterengagement and is held fixed by adjustment means.

6. The combination of claim 1 wherein the coextensive face at theopposite side of the ring gear is in a plane normal to the axis ofrotation of said ring gear and the thrust face of the side thrustlimiter bearing is held juxtapposed parallel thereto by adjustmentmeans.

7. The combination of claim 1 wherein the coextensive face at theopposite side of the ring gear is in a plane normal to the axis ofrotation of said ring gear and the thrust face of the side thrustlimiter bearing is held juxtapposed opposite the load center of the ringand pinion interengagement and parallel thereto by adjustment means.

8. In combination with a transmission case having a center sectionclosed by opposite side plates assembled therewith and having bearingscarried thereby joumaling a ring gear on a rotational axis and saidcenter section having bearings carried thereby journaling a pinion gearon a rotational axis angularly related to said ring gear axis, saidgears being journaled in the case to take the normal axial and radialthrust loads and the ring gear having a circumferentially disposedmarginal portion intermeshed with the pinion gear at one side and acoextensive face at the opposite side; a side thrust limiter engageablewith said opposite side face to prevent separation of the intermeshedgears by restricting lateral deflection at the marginal portion of saidring gear and comprising a bearing with a thrust face carried by one ofsaid side plates and positioned thereby in close proximity to thecoextensive face at the opposite side of said marginal portion of thering gear, thereby reinforcing the combination against thrust loadscausing lateral deflection of the marginal portion of the ring gear andinterface engagement of said opposite side face thereof with said sidethrust limiter.

9. The combination of claim 8 wherein the side thrust limiter ispositioned by said one side plate opposite the load center of the ringand pinion interengagement.

10. The combination of claim 8 wherein the coextensive face at theopposite side of the ring gear is in a plane normal to the axis ofrotation of said ring gear and the thrust face of the side thrustlimiter bearing is positioned by said one side plate and juxtapposedparallel to said coextensive face.

11. The combination of claim 8 wherein the coextensive face at theopposite side of the ring gear is in a 7 plane normal to the axis ofrotation of the said ring gear and the thrust face of the side thrustlimiter bearing is positioned by said one side plate juxtapposedopposite the load centerof the ring and pinion interengagement parallelto said coextensive face.

12. The combination of claim 8 wherein the side thrust limiter ispositioned by said one side plate opposite the load center of the ringand pinion interengagement and is held fixed by adjustment means.

13. The combination of claim 8 wherein the coextensive face at theopposite side of the ring gear is in a plane normal to the axis ofrotation of said ring gear and the thrust face of the side limiterbearing is held positioned by said one side plate and juxtapposedparallel to said coextensive face by adjustment means.

14. The combination of claim 8 wherein the coextensive face at theopposite side of the ring gear is in a plane normal to the axis ofrotation of said ring gear and the thrust face of the side thrustlimiter bearing is held bysaid one side plate and juxtapposed oppositethe load center of the ring and pinion interengagement and parallel tosaid coextensive face by adjustment means.

15. In combination with a transmission case having a center section withspaced planar ends closed by opposite side plates assembled therewithand having bearings carried thereby journaling a ring gear on arotational axis and said center section having a boss with bearingscarried thereby journaling a pinion gear on a rotational axis angularlyrelated to said ring gear axis, said gears being journaled in the caseto take the normal axial and radial thrust loads, the ring gear having acircumferentially disposed marginal portion inter meshed with the piniongear at one side and a coextensive face at the opposite side; a sidethrust limiter engageable with said opposite side face to preventseparation of the intermeshed gears by restricting lateral deflection atthe marginal portion of said ring gear and comprising a bearing with athrust face carried by one of said side plates and positioned thereby inclose proximity to the coextensive face at the opposite side of saidmarginal portion of the ring gear, said boss having interface engagementwith the other side plate thereby reinforcing the combination againstthrust loads causing lateral deflection of the marginal portion of thering gear and interface engagement of said opposite side face thereofwith said side thrust limiter.

16. The combination of claim 15 wherein the side thrust limiter ispositioned by said one side plate and the said boss is positioned bysaid other side plate and in each instance opposite the load center ofthe ring and pinion interengagement.

17. The combination of claim 15 wherein the coextensive face at theopposite side of the ring gear is in a plane normal to the axis ofrotation of said ring gear and the thrust face of the side thrustlimiter bearing is positioned by said one side plate and juxtapposedparallel to said coextensive face.

18. The combination of claim 15 wherein the coextensive face at theopposite side of the ring gear is in a plane normal to the axis ofrotation of said ring gear and the thrust face of the side thrustlimiter bearing is positioned by said one side plate and the said bossis positioned by said other side plate and in each instance opposite theload center of the ring and pinion interengagement.

19. The combination of claim 15 wherein the side thrust limiter ispositioned by said one side plate and the said boss by the other sideplate and in each instance opposite the load center of the ring andpinion interengagement, said side thrust limiter being fixed in positionby adjustment means.

20. The combination of claim 15 wherein the coextensive face at theopposite side of the ring gear is in a plane normal to the axis ofrotation of said ring gear and the thrust face of the side limiterbearing is held positioned by said one side plate and the said boss bythe other side plate, said side thrust limiter being fixed in positionby adjustment means.

means.

1. In combination with a transmission case having a ring gear and apinion gear, said ring and pinion gears being rotatably journaled inbearings carried in the case to take the normal axial and radial thrustloads, the ring gear having a circumferentially disposed marginalportion intermeshed with the pinion gear at one side and a coextensiveface at the opposite side; and a side thrust limiter engageable withsaid opposite side face to prevent separation of the intermeshed gearsby restricting lateral deflection at the marginal portion of said ringgear and comprising a bearing with a thrust face positioned in closeproximity to the coextensive face at the opposite side of said marginalportion of the ring gear, thereby reinforcing the combination againstthrust loads causing lateral deflection of the marginal portion of thering gear and interface engagement of said opposite side face thereofwith said side thrust limiter.
 2. The combination of claim 1 wherein theside thrust limiter is positioned opposite the load center of the ringand pinion interengagement.
 3. The combination of claim 1 wherein thecoextensive face at the opposite side of the ring gear is in a planenormal to the axis of rotation of said ring gear and the thrust face ofthe side thrust limiter bearing is juxtapposed parallel to saidcoextensive face.
 4. The combination of claim 1 wherein the coextensiveface at the opposite side of the ring gear is in a plane normal to theaxis of rotation of the said ring gear and the thrust face of the sidethrust limiter bearing is juxtapposed opposite the load center of thering and pinion interengagement parallel to said coextensive face. 5.The combination of claim 1 wherein the side thrust limiter is positionedopposite the load center of the ring and pinion interengagement and isheld fixed by adjustment means.
 6. The combination of claim 1 whereinthe coextensive face at the opposite side of the ring gear is in a planenormal to the axis of rotation of said ring gear and thE thrust face ofthe side thrust limiter bearing is held juxtapposed parallel thereto byadjustment means.
 7. The combination of claim 1 wherein the coextensiveface at the opposite side of the ring gear is in a plane normal to theaxis of rotation of said ring gear and the thrust face of the sidethrust limiter bearing is held juxtapposed opposite the load center ofthe ring and pinion interengagement and parallel thereto by adjustmentmeans.
 8. In combination with a transmission case having a centersection closed by opposite side plates assembled therewith and havingbearings carried thereby journaling a ring gear on a rotational axis andsaid center section having bearings carried thereby journaling a piniongear on a rotational axis angularly related to said ring gear axis, saidgears being journaled in the case to take the normal axial and radialthrust loads and the ring gear having a circumferentially disposedmarginal portion intermeshed with the pinion gear at one side and acoextensive face at the opposite side; a side thrust limiter engageablewith said opposite side face to prevent separation of the intermeshedgears by restricting lateral deflection at the marginal portion of saidring gear and comprising a bearing with a thrust face carried by one ofsaid side plates and positioned thereby in close proximity to thecoextensive face at the opposite side of said marginal portion of thering gear, thereby reinforcing the combination against thrust loadscausing lateral deflection of the marginal portion of the ring gear andinterface engagement of said opposite side face thereof with said sidethrust limiter.
 9. The combination of claim 8 wherein the side thrustlimiter is positioned by said one side plate opposite the load center ofthe ring and pinion interengagement.
 10. The combination of claim 8wherein the coextensive face at the opposite side of the ring gear is ina plane normal to the axis of rotation of said ring gear and the thrustface of the side thrust limiter bearing is positioned by said one sideplate and juxtapposed parallel to said coextensive face.
 11. Thecombination of claim 8 wherein the coextensive face at the opposite sideof the ring gear is in a plane normal to the axis of rotation of thesaid ring gear and the thrust face of the side thrust limiter bearing ispositioned by said one side plate juxtapposed opposite the load centerof the ring and pinion interengagement parallel to said coextensiveface.
 12. The combination of claim 8 wherein the side thrust limiter ispositioned by said one side plate opposite the load center of the ringand pinion interengagement and is held fixed by adjustment means. 13.The combination of claim 8 wherein the coextensive face at the oppositeside of the ring gear is in a plane normal to the axis of rotation ofsaid ring gear and the thrust face of the side limiter bearing is heldpositioned by said one side plate and juxtapposed parallel to saidcoextensive face by adjustment means.
 14. The combination of claim 8wherein the coextensive face at the opposite side of the ring gear is ina plane normal to the axis of rotation of said ring gear and the thrustface of the side thrust limiter bearing is held by said one side plateand juxtapposed opposite the load center of the ring and pinioninterengagement and parallel to said coextensive face by adjustmentmeans.
 15. In combination with a transmission case having a centersection with spaced planar ends closed by opposite side plates assembledtherewith and having bearings carried thereby journaling a ring gear ona rotational axis and said center section having a boss with bearingscarried thereby journaling a pinion gear on a rotational axis angularlyrelated to said ring gear axis, said gears being journaled in the caseto take the normal axial and radial thrust loads, the ring gear having acircumferentially disposed marginal portion intermeshed with the piniongear at one side and a coextensive face at the opposite side; a sidethrust limiter engageable with said opposite side face to preventseparation of the intermeshed gears by restricting lateral deflection atthe marginal portion of said ring gear and comprising a bearing with athrust face carried by one of said side plates and positioned thereby inclose proximity to the coextensive face at the opposite side of saidmarginal portion of the ring gear, said boss having interface engagementwith the other side plate thereby reinforcing the combination againstthrust loads causing lateral deflection of the marginal portion of thering gear and interface engagement of said opposite side face thereofwith said side thrust limiter.
 16. The combination of claim 15 whereinthe side thrust limiter is positioned by said one side plate and thesaid boss is positioned by said other side plate and in each instanceopposite the load center of the ring and pinion interengagement.
 17. Thecombination of claim 15 wherein the coextensive face at the oppositeside of the ring gear is in a plane normal to the axis of rotation ofsaid ring gear and the thrust face of the side thrust limiter bearing ispositioned by said one side plate and juxtapposed parallel to saidcoextensive face.
 18. The combination of claim 15 wherein thecoextensive face at the opposite side of the ring gear is in a planenormal to the axis of rotation of said ring gear and the thrust face ofthe side thrust limiter bearing is positioned by said one side plate andthe said boss is positioned by said other side plate and in eachinstance opposite the load center of the ring and pinioninterengagement.
 19. The combination of claim 15 wherein the side thrustlimiter is positioned by said one side plate and the said boss by theother side plate and in each instance opposite the load center of thering and pinion interengagement, said side thrust limiter being fixed inposition by adjustment means.
 20. The combination of claim 15 whereinthe coextensive face at the opposite side of the ring gear is in a planenormal to the axis of rotation of said ring gear and the thrust face ofthe side limiter bearing is held positioned by said one side plate andthe said boss by the other side plate, said side thrust limiter beingfixed in position by adjustment means.
 21. The combination of claim 15wherein the coextensive face at the opposite side of the ring gear is ina plane normal to the axis of rotation of said ring gear and the thrustface of the side limiter bearing is held positioned by said one sideplate and the said boss by the other side plate, and in each instanceopposite the load center of the ring and pinion interengagement, saidside thrust limiter being fixed in position by adjustment means.